Does it actually matter? - has anyone ever been penalized for driving on a foreign driving license beyond the 90 days period? You can only get full insurance with a DR license anyway so it doesn't matter how "expired" the foreign license is, to them your canadian license is invalid from day one, - just get la ley insurance with casa de conductor and drive carefully. If you are using a foreign insurance somehow, they aren't going to care about the 90 days either. One time I was driving a car rental (about 4 months into my stay in DR), had the insurance via my credit card and had an accident (100% the other guys' fault but what does it matter in DR). Neither the police nor my insurance company (TD Insurance) had the slightest interest in how long I had been in the country.
I don't see how keeping the license "current" by re-entering the country is going to make anyone's life easier - better to save the flight costs and use it towards the car repair for if/when you need them.
